What is the proper way to detect the presence of window.console?

Question

I have this bit of code:

            var has_logger = (window.console && window.console.log);
            if (has_logger) {
                window.console.log(data);
            }

has_logger, instead of being a boolean value, is actually initialised to a function object ( function log() { [native code] } )

My questions:

• There is no need to test for the console.log in modern browsers, correct?

• What is the proper way to initialize has_logger to a boolean value instead of a function object?

Answer 1

If Firebug is not enabled, Firefox will throw an error if you don't check.

var has_logger = !!(window.console && window.console.log);

will always be Boolean.

Answer 2

Yes, that's a perfectly fine way to test, and yes you do have to test. Note that your has_logger variable actually ends up with a reference to the function, so you could turn it into a boolean using the double-bang as Amadan said.

Beware of IE9's odd behavior around console.log, though.

If you want your code to work in other JavaScript environments than browsers, though, you might use this:

has_logger = typeof console === "object" && console.log;

You can safely test the type of a free reference even if it's not defined. That will work in browsers (where you have window) and other environments (where you don't).